Safety razor blades



United States Patent O 3,425,877 SAFETY RAZOR BLADES Roger FrederickDeacon, Richmond, Surrey, England,

assignor to Wilkinson Sword Limited, London, England,

a British company, and Uddehohns Aktiebolag, Uddeholm, Sweden, a Swedishjoint-stock company No Drawing. Filed Oct. 22, 1965, Ser. No. 502,460

US. Cl. 148-12.4 6 Claims Int. Cl. C2111 7/14, 9/18 ABSTRACT OF THEDISCLOSURE Razor blade strip is manufactured from a corrosionresistantstainless steel having a chromium content of from 10.0 to 20.0%, thecomposition being such that it can be annealed to form austenite andthereafter cooled to an elevated temperature at which the austenite ismetasta- 'ble. At this elevated temperature each edge region of thestrip where a cutting edge is required is subjected to a substantialcross-sectional reduction to deform the austenite, strip being cooledthereafter to transform the deformed austenite to martensite.

This invention relates to methods of manufacturing razor blade strip andto razor blades produced from such strip.

According to the present invention there is provided a method ofmanufacturing razor blade strip from a steel containing metastableaustenite at an elevated temperature, wherein at least one edge of thestrip is submitted to cross-sectional reduction at said temperature todeform the austenite and the strip is subsequently cooled to transformthe deformed austenite to martensite.

The present invention also provides a method of manufacturing razorblade strip from steel whose composition is such that it can be annealedto form austenite and thereafter cooled to an elevated temperature atwhich the austenite is metastable, wherein deformation is effected atthis temperature, at least in the region where a cutting edge is to beformed, and the strip then cooled to convert at least partially thedeformed austenite in said region to martensite.

The present invention further provides a method of manufacturing razorblade strip from a steel whose composition and treatment is such that ata predetermined elevated temperature the steel contains metastableausten ite, comprising effecting a cross-sectional reduction of one orboth edges of the strip at said elevated temperature to deform theaustenite in the region of the edge or edges, cooling to effecthardening of the strip, by transformation of the deformed austenite tomartensite the subsequent formation of the cutting edge or edges beingat least partly effected by an electrolytic process.

One method of manufacturing razor blade strip in accordance with thepresent invention will now be described, by way of example.

The steel used must be one whose composition is such that it can beannealed to form austenite, generally at temperatures within the range800 to 1200 C., the austenite being metastable after cooling to atemperature which will generally be within the range 300 to 800 C. Thedetailed composition of such steels will be considered in greater detailbelow.

Strip of such a steel is formed to the required final blade shape, thatis to say without the cutting edge or cutting edges formed thereon butwith what will eventually be the individual blades joined end-to-end.Such formation may, for example, be effected by punching and may includeformation of a central slot where doubleedged blades are to be produced.Such strip is fed into 3,425,877 Patented Feb. 4, 1969 an austenitisingfurnace in which it is heated to the austenitising temperature. From thefurnace the strip is passed through a cooling muffie to cool it to atemperature at which the austenite is metastable, the cooling rate beingcontrolled to avoid any undesired transformation of the austenite. Fromthe cooling muffle the strip is passed to a press maintained at anelevated temperature at which the austenite is still metastable, forexample within the range 300 to 800 C. The atmosphere may be controlledthroughout the passage of the strip through the austenitising furnace,the cooling mufile and the press and may be an inert or reducingatmosphere, for example of cracked ammonia. In the press the edges ofthe blade are deformed by the use of suitable dies or other means toform at least partly the required cross section for the cutting edges.On cooling the deformed austenite is transformed to martensite withconsequent increase in the eventual hardness of the cutting edges.

Pressing may be limited to the cross-sectional area reduction necessaryto give the requisite hardness increment or may be continued to give arelatively fine cutting edge requiring little subsequent finishing. Theresultant included angle of the finished edge may for example be aslittle as 10 to 14.

On leaving the press the strip is hardened by quenching to roomtemperature, for example by passage between Water cooled chill blocks,by natural cooling in still air or by quenching in water, oil or othersuitable liquids. Optionally, to increase the hardness and convert atleast some of any retained austenite to martensite, further coolingsubstantially below room temperature may be effected, for example tominus 78 C.

It will be understood that the deformation of austenite at the elevatedtemperature may be effected by subjecting the whole strip to reductionof cross-sectional area, for example by rolling or forging, in whichcase the reduction will replace some of the normal cold rollingreduction. The degree of deformation should preferably exceed 30% andmay rise to as high at The precise temperature at which deformation iseffected is governed by the amount of improvement required and the typeof equipment available to effect the deformation. In this connection itwill be appreciated that a greater force will be required for a givenreduction at lower temperatures but that a greater increase in hardnesswill result from effecting the deformation at lower temperatures. By wayof example it may be stated that typical values of temperature for theaustenitising furnace (T1) and the press (T2) for the steels specifiedare as follows:

After hardening, the formation or finishing (the latter case being whenthe edge has been partly formed during deformation at elevatedtemperatures) of the cutting edge or edges may be effected byconventional methods or by electrolytic processing such as described inour co-pending patent application No. 30,658 of 1963 and cognate No.20,032 of 1964.

Considering now in greater detail the steels which may be used for thepresent invention it will be appreciated that their composition must besuch that the steel :can be cooled to the deformation temperaturewithout transforming to ferrite. Suitability of any given steel canusually be assessed by a metallurgist, particularly with the aid of anisothermal transformation diagram, but of course in cases of doubt thesuitability can readily be determined experimentally.

Examples of steels which have improved properties after such hotdeformation, by comparison with their properties after conventional heattreatment, are those known as hot work die steels as for instance AlSl,type No. H11. Other examples are those steels usually known as 43XXtypes, as for instance AlSl type No. 4340, and ultra-high strengthsteels such as for instance Ladish D6A, Labelle H.T. and Supertricent.Further examples are British Standards Specification 970 types Nos. EN.24, EN. 30A and EN. 30B. Examples of corrosion resistant steels to whichimproved properties can be imparted are alloys based on iron andcontaining 10-20%- by weight of chromium. They may, in addition, contain-2% carbon, 03% nickel, 04% molybdenum, 04% manganese, 04% copper, 010%cobalt, 03% tungsten, 0-2% vanadium, 03% silicon, together with theusual adventitious amounts of phosphorous and sulphur. Examples ofmaterials of this type are those conforming to British StandardsSpecification 970 types EN. 56 and EN. 57 and those known as AlSl typesNos. 410, 403, 41 4, 416,

4 annealing the strip at a first temperature within the range 800 to1200 C., cooling the annealed strip to a second temperature within therange 300 to 800 C. at which the austenite in the strip is metastable,effecting a cross-sectional reduction of one edge of the strip whilstthe strip is maintained at said second temperature to give said edge aprofile substantially that of the desired final cutting edge, coolingthe strip to room temperature, finishing said edge of the strip to acutting edge, and severing the strip transversely to form razor blades.4. The manufacture of razor blades from austenitic steel strip, saidstrip containing at least 13% by weight of chromium, comprising thesteps of annealing the strip at a first temperature within the range1000 to 115 0 C.,

cooling the annealed strip to a second temperature within the range 550to 650 C. at which the austenite 418, 420, 431, 440A and 440C. Otherexamples are those f SHIP metatable: steels made by Uddeholm g and idtifi d by them effecting a cross-sectional reduction of between asnumbers ss1, S5716, ss731, AEB, SS6, SSB6 and and 95% of one edge of thestrip whilst the strip i Orvar II, maintained at said secondtemperature,

Specific compositions of some of the above mentioned 25 Cooling thestrip to at least room tfimperatufc, steels (in percent by weight) areas follows: sharpening said edge of the strip to a cutting edge, and

0 Mn si Cr Mo Ni v Ladish DGA 0. 75 0. 22 1. 0 Labelle HT... 0. 43 1. 2.25 1. 35 Supertricent. 0. 55 0. 8 2. 0. 9 Uddeholm ss1. 0.10 0. 45 0.13. 7 Uddeholm $8716-. 0.35 0.45 0.45 13.6 Uddeholm ss731.. 0. 22 0.0.30 13. 2 Uddeholm AEB.. 0. 95 1. 05 0.18 13. 5 Uddeholm 856.-.. 0. 320. 45 0. 40 0. 40 Uddeholm SSB6 0.40 0. 37 0. 37 14.0 Uddeholm Orvar I0. 37 0. 45 1.00 5. 3

By means of the present invention it is possible to produce razor bladeshaving a cutting edge which is harder than when the same or a similarsteel is conventionally treated. This is particularly advantageous whena subsequent coating process, such as a polymer coating, involvesheating which is liable to reduce the hardness of the cutting edges.Furthermore there is normally an increase in properties such astoughness, fatigue strength and proof stress which permit the productionof an improved edge.

It will be appreciated that the strip may be severed transversely toform the individual razor blades either before or after the final stageof formation of the cutting edge or edges.

I claim:

1. In the manufacture of razor blade strip from a stainless steel havinga chromium content of from approximately 10.0% and which containsmetastable austenite at an elevated temperature, the steps of submittingan edge region only of the strip to crosssectional reduction at saidelevated temperature to deform the austenite, and, thereafter,

cooling the strip to transform the deformed austenite to martensite.

2. In the manufacture of razor blade strip from corrosion-resistantstainless steel alloy having a chromium content of from 10.0 to 20.0%and whose composition is such that it can be annealed to form austeniteand thereafter cooled to an elevated temperature at which the austeniteis metastable the steps of effecting deformation of the strip at thiselevated temperature, in each region where a cutting edge is to beformed and, subsequently,

cooling said strip to convert at least partially to martensite theaustenite in the deformed region.

3. The manufacture of razor blades from a strip of corrosion-resistantaustenitic stainless steel alloy having a chromium content of at least10.0% comprising the steps of severing the strip transversely intoindividual razor blades. 5. The manufacture of razor blades as claimedin claim 4, wherein said strip is cooled to a temperature substantiallybelow room temperature.

6. The manufacture of razor blades from corrosion resistant austeniticsteel strip, said strip being of a steel alloy containing by weightpercentages of 1020% chromium, up to 2% carbon, up to 3% nickel, up to4% molybdenum, up to 4% manganese, up to 4% copper, up to 10% cobalt, upto 3% tungsten, up to 2% vanadium and up to 3% silicon, comprising thesteps of annealing the strip at a first temperature within the range 800to 1200" C.,

cooling the annealed strip to a second temperature within the range 300to 800 C. at which the austenite in the strip is metastable,

deforming each edge of the strip whilst the strip is maintained at saidsecond temperature, said deformation giving each edge a cross-sectionalprofile approximating to the desired final edge shape,

cooling the strip to room temperature,

electrolytically finishing said edge of the strip to a cutting edge, and

severing the strip transversely to form razor blades.

References Cited UNITED STATES PATENTS 2,934,463 4/1960 Schmatz et al.148-124 3,210,221 10/1965 Nachtman et al 14812.4 3,215,565 11/1965Harvey 14812.4 3,240,634 3/1966 Nachtman l48--l2.4 3,340,102 9/1967Kulin et al. 14812.4

HYLAND BIZOT, Primary Examiner.

WAYLAND W. STALLARD, Assistant Examiner.

